Process for manufacturing a microcircuit cochlear electrode array

ABSTRACT

A process for manufacturing a single microcircuit into an integrated cochlear electrode array includes securing and supporting a nonconductive film substrate; attaching a metallic ribbon to a surface of the substrate; machining a flat multiconductor microcircuit from the ribbon to produce a flat elongated multiconductor tail portion with spaced outwardly exposed electrode receiving pads, and a flat multiconductor head portion connected to the tail portion and having spaced outwardly exposed attachment pads; laminating the flat microcircuit between the film substrate and an insulating cover; excising the laminated microcircuit from the film substrate with the electrode receiving pads exposed; wrapping the tail portion of the excised laminated microcircuit into a helix with the exposed electrode receiving pads wrapped around the insulating cover; mounting and electrically connecting the ring electrodes on and to the exposed electrode pads; and overmolding the helix tail portion with a polymeric material to ready the microcircuit for cochlear implant.

RELATED PATENT APPLICATION

The present invention claims the benefit of U.S. Provisional PatentApplication Ser. No. 61/023,389 filed Jan. 24, 2008, which isincorporated herein by reference.

BACKGROUND OF INVENTION

Current procedures for manufacturing cochlear electrodes involveoperator intervention throughout much of the manufacturing processwherein the electrodes are manually formed and handled. This results inrelatively slow processing of the electrodes and subjects the electrodesto undesired mechanical stresses and breakage.

It is an object of the present invention to provide a more compact androbust cochlear electrode design and a more rapid process of manufacturethat reduces operator intervention, reduces material waste and rework ofthe electrodes and increases the throughput and efficiency of electrodemanufacture.

SUMMARY OF INVENTION

The present invention is directed to a microcircuit integrated cochlearelectrode array and a process for manufacturing the electrode.

Basically, the microcircuit comprises flat multiconductor head and tailportions. The multiconductor head portion has spaced outwardly exposedcircuit attachment pads. The flat multiconductor tail portion ishelically wrapped with spaced electrode attachment pads on an exposedouter surface thereof. Ring electrodes are carried by the helicallywrapped tail portion and extend around and are electrically connected tothe electrode receiving pads and overmolded with a suitable polymericmaterial. Further, the tail and head portions preferably are laminatedbetween a nonconductive film substrate and an insulating cover and aportion of the tail portion is unwrapped to define a lateral offsetforming a stylet receiving lumen for a balance of the helically wrappedtail portion. As used herein, the term “ring electrode” is intended toinclude both circumferentially closed and circumferentially openconductive rings dimensioned to receive and be supported by andelectrically connected to the electrode receiving pads on the exposedouter surface of the helically wrapped flat multiconductor tail portion.Also, as used herein, the term “overmolded” as applied to the ringelectrodes is intended to encompass all known molding processes andprocedures employed in the coating of cochlear electrodes with asuitable polymeric material, including, without limitation, thepre-coating masking of portions of such electrodes followed by a removalof the masking material to expose portions of the electrode, the coatingof the electrodes using molding equipment including internal featuresthat block the flow of the polymeric material to portions of theelectrode leaving the electrode with exposed portions, and thepost-coating use of polymeric material removal apparatus such as lasersto remove some of the coating to expose portions of the electrode.

Basically a process for manufacturing and processing the microcircuitintegrated cochlear electrode array comprises the steps of securing andsupporting a nonconductive film substrate, attaching a metallic ribbonto a surface of the substrate and machining a flat multiconductormicrocircuit from the ribbon. The machined microcircuit includes (i) aflat elongated multiconductor tail portion with spaced outwardly exposedelectrode receiving pads and (ii) a flat multiconductor head portionconnected to the tail portion and having spaced vertically exposedcircuit attachment pads. The flat microcircuit is laminated between thesubstrate and an insulating cover and the laminated microcircuit is thenexcised from the remaining film substrate with the electrode receivingpads exposed. The tail portion of the excised laminated microcircuit isthen helically wrapped into a helix with the exposed electrode receivingpads extending around the insulating cover. Finally, ring electrodes aremounted on and electrically connected to the exposed electrode pads andthe helically wrapped tail portion is overmolded with a suitablepolymeric or plastic material readying the microcircuit for cochlearimplant.

BRIEF DESCRIPTION OF ACCOMPANYING DRAWINGS

FIG. 1A is a flow chart of the basic steps central to the manufacturingprocess of the present invention.

FIG. 1B shows a basic form of a lower frame of a carrier utilized in theprocess steps of securing and supporting a nonconductive film substrate.

FIG. 2 shows a length of the nonconductive film substrate extending froma roll over the lower frame of FIG. 1B.

FIG. 3 shows the length of film substrate after it has been lowered ontothe lower frame and releasably secured thereto by attachment meansextending vertically from the lower frame.

FIG. 4 shows the length of film substrate clamped and secured betweenthe lower frame and an upper frame of the carrier.

FIG. 5 shows the length of film substrate secured by the carrier afterall excess film has been trimmed from the carrier and the roll of filmhas been removed.

FIG. 6 shows the carrier and film substrate of FIG. 5 with a flatmetallic ribbon attached to an upper surface of the film.

FIG. 7 shows two laterally spaced longitudinally extendingmulticonductor microcircuits machined by laser cutting the metallicribbon attached to the upper surface of the film substrate shown in FIG.6, each microcircuit including a flat elongated multiconductor tailportion with longitudinally spaced outwardly exposed ring electrodereceiving pads and a flat multiconductor arc-shaped head portion withspaced circuit attachment or interconnect pads as shown more clearly inFIG. 7A and FIG. 7B respectively, FIG. 7C showing the close lateralspacing of laser cut individual conductors in the tail portion of themicrocircuits.

FIG. 8 shows the carrier and microcircuits of FIG. 7 clamped to a baseof a heated ceramic vacuum chuck prior to overmolding with a siliconelayer.

FIG. 9 shows the carrier and chuck of FIG. 8 with an overmold platecovering the carrier and including lower features that shut-off andcreate exposed areas on the ring electrode receiving pads andinterconnect pads.

FIG. 10 shows the carrier and microcircuits of FIG. 8 after theovermolding step has been completed and the microcircuits are laminatedbetween the silicone layer and the film substrate.

FIG. 11 shows the carrier and laminated microcircuits removed from theceramic vacuum chuck of FIGS. 8-10.

FIG. 12 shows the microcircuits completely excised from the carrier asby laser cutting through both the silicone and film substrate layers.

FIG. 13A shows the head portion of one of the microcircuits clamped to atooling bow having a tensioned wire extending between ends of the bowand used first to receive a series of platinum electrode rings and thenafter tensioning by the bow to receive the tail of the microcircuit asit is wrapped into a helical shape and to suspend the microcircuitduring subsequent overmolding processes.

FIG. 13B shows the head portion of the microcircuit extending from thetensioned wire of the tooling bow and the tail portion wrapped in ahelix around the tensioned wire with the ring electrode receiving padsexposed on an outer surface of the helix.

FIG. 14A shows the head and tail portions of the microcircuit asillustrated in FIG. 13B with a ring electrode being positioned over anexposed receiving pad of the microcircuit.

FIG. 14B shows a series of ring electrodes on the helically wrapped tailportion of the microcircuit each ring being positioned over a differentelectrode receiving pad with a hole in the ring electrode aligned withits supporting pad for future laser welding to the pad.

FIG. 14C in an enlarged showing of a portion of the helically wrappedportion of FIG. 14B depicting each electrode as laser welded to itssupporting pad.

FIG. 15 shows the microcircuit supported on the tensioning wire of thetooling bow after a first overmold that encapsulates the wrappedelectrode up to its first ring electrode and the underneath of theinterconnect circuit of the head portion of the microcircuit creating asilicone stand-off for the head portion.

FIG. 16 shows the microcircuit supported on the tensioning wire of thetooling bow after a second overmold that encapsulates the wrappedelectrode out to the end of the electrode subassembly with the overmolddecreasing in diameter as it approaches the first visible ringelectrode.

FIG. 17A shows the overmolded electrode subassembly of FIG. 16 aftercompletion of a third overmolding process that was preceded by thesubassembly having been removed from the tooling bow and an end of themicrocircuit unwrapped offsetting the electrode and creating a styletlumen into which a stylet was placed and the electrode and stylet placedinto overmold tooling for overmolding.

FIG. 17B is an enlarged showing of a portion of the electrode assemblyof FIG. 17A including the unwrapped microcircuit and stylet lumen.

FIG. 18A a conventional stylet insertion tool inserted into the lumen ofthe electrode subassembly straightening the electrode for insertion.

FIG. 18B shows the stylet insertion tool rotated 90 degrees to show thehandle of the tool.

FIG. 19 shows the completed helix electrode assembly ready forattachment of its head portion to the platinum feedthrough posts of atitanium housing as shown in FIGS. 20A and 20B.

FIGS. 20A and 20B show a titanium housing where the microcircuitinterconnect pads slit slightly during laser machining make intimatecontact with corresponding ones of the feedthrough posts for laserwelding to the posts.

DETAILED DESCRIPTION OF INVENTION

As shown in FIG. 19, the process of the present invention is intended toefficiently produce a new and improved microcircuit integrated cochlearelectrode array 10, that comprises multiconductor microcircuit 12including a multiconductor tail portion 14 with longitudinally spacedoutwardly exposed electrode receiving pads 16 (see FIGS. 7A and 12) anda flat multiconductor head portion 18 connected to the tail portion andhaving spaced outwardly exposed circuit attachment pads 20 (see FIGS.13B, 15, 19, 20A and 20B). The tail and head portions 14 and 18 arelaminated between a nonconductive film substrate 22 (see FIGS. 3-5) andan insulating cover 24 (see FIG. 10). As shown in FIGS. 14C and 17B, thetail portion 14 is helically wrapped into a helix with the electrodereceiving circuit attachment pads 16 exposed to and carrying ringelectrodes 26 overmolded with a plastic material 28 (see FIG. 17A). Asalso shown in FIGS. 17A and 17B, a portion of the tail portion 14 may beunwrapped at a junction 58 with a section 60 including the ringelectrodes 62 offsetting an electrode section 49 and creating a lumen 62for receiving a stylet 64 as shown in FIGS. 18A and 18B.

To produce such an electrode array, the process of the present inventionbasically comprises the steps of the flow diagram of FIG. 1A. Asrepresented in FIG. 1A, and as illustrated in accompanying FIGS. 1B-20B,the process comprises securing and supporting the nonconductive filmsubstrate 22; attaching a metallic ribbon 30 to a surface of thesubstrate 22; machining at least one flat multiconductor microcircuit 12from the ribbon 30 including the flat elongated multiconductor tailportion 14 with longitudinally spaced outwardly exposed ring electrodereceiving pads 16 and the flat multiconductor head portion 18 connectedto the tail portion and having spaced outwardly exposed attachment pads20; laminating the flat microcircuit 12 between the film substrate 22and the insulating cover 24; excising the laminated microcircuit 12 fromthe film substrate 22 with the electrode receiving pads 20 exposed;helically wrapping the tail portion 14 of the excised laminatedmicrocircuit 12 into a helix with the exposed electrode receiving pads16 wrapped around the insulating cover 24; mounting and electricallyconnecting the ring electrodes 26 on and to the exposed electrode pads16; and overmolding the helically wrapped tail portion 14 with theplastic material 28 to ready the microcircuit for cochlear implant.

With regard to the securing of the nonconductive film substrate 22 and ashown in FIGS. 1B-5, a roll 32 of the nonconductive film substrate 22,such as a roll of nonconductive plastic, is positioned adjacent an endof a lower open frame 34 of a carrier 36 utilized in the process stepsof securing and supporting the nonconductive film substrate.

As represented in FIG. 2, a length of the film substrate 22 is drawnfrom the roll 32 to extend over the top of the open frame 34.Preferably, the film substrate 22 is maintained under tension in both Xand Y directions while positioned over the open frame.

As represented in FIG. 3, the length of film substrate 22 is then moveddownward relative to the lower open frame 34 until attachment means 38,such as upwardly projecting pins 39, engage and penetrate a lowersurface of the film substrate securing the tensioned length of filmsubstrate 22 to the lower open frame.

As represented in FIG. 4, an upper open frame 40 of the carrier 36 isthen positioned over and on the lower open frame 34 with alignment holes41 in the upper frame receiving alignment pins 35 extending upward fromthe lower frame 34 and the upper frame secured to the lower frame as byscrews clamping the length of tensioned film substrate within thecarrier 36. Excess film is then trimmed from the carrier 36 andseparated from the roll 32 of plastic as depicted in FIG. 5.

As indicated in FIG. 1A, after the film substrate has been secured andsupported, the next step in the process of the present invention is theattachment of the flat metallic ribbon 30 to a surface of the filmsubstrate 22 shown in FIG. 6. In practice this is accomplished byplacing the carrier 36 and the metallic ribbon 30, preferably a platinumiridium ribbon, into a standard plasma etching machine (not shown) wheremating surfaces of the film substrate 22 and the ribbon 30 are etched.The carrier 36 and the etched platinum ribbon 30 are then placed into astandard thermal heating fixture (not shown) with tooling liners locatedon the carrier. In this regard, the platinum ribbon 30 is carefullyplaced into a transfer fixture (not shown) so that the ribbon is alignedrelative to the tooling liners located on the carrier 36. Uponactivation of the of the transfer fixture, the ribbon 30 is lowered ontothe etched surface of the film substrate 22 where pressure and heat areapplied for a prescribed time period to secure the ribbon to the filmsubstrate.

Once the platinum ribbon 30 is secured to the film substrate 22, one ormore flat multiconductor microcircuits 12 of the previously describedstructure are machined from the ribbon as depicted in FIGS. 7, 7A and7B; FIG. 7C depicting the spacing of the parallel laser machinedconductors of the two microcircuits 12 as being approximately 25 micronin width with 25 micron kerfs between the conductors. Preferably, themachining is achieved using laser machining with a femtosecond impulselaser machining center such as the commercially available Clark-MXRFemtosecond Impulse Laser Machining Center.

By way of comparison, traditional lasers first melt the material beingmachined and then vaporize it. Femtosecond laser light pulses are aboutone quadrillionth of a second in time duration and bypass the materialmelt phase and transition directly into the vapor phase thus creatingvery little heat and no slag or damage to surrounding areas. Also,femtosecond light pulses are capable of creating sub-micron featuresdown to 50 nm and are wavelength independent and capable of machiningany material.

After the microcircuits 12 are laser machined in the ribbon 30, theupper surface of the platinum ribbon is plasma etched and the carrier 36is placed on a conventional heated ceramic vacuum chuck 42 and clampedin place as shown in FIG. 8 for conventional overmolding and laminationof the microcircuits between the film substrate 22 and the previouslyreferenced insulating cover 24. In these regards, and as represented inFIG. 9, an overmolding mold plate 44 is installed over the exposedmicrocircuits 12 using tooling pins (not shown) located on a top coverof the carrier 36. The mold plate 44 is designed with shut-off featuresthat will expose the ring electrode receiving pads 16 and theinterconnect pads 20 during the subsequent operation of the heatedvacuum chuck 42 and lamination of the microcircuits between the filmsubstrate 22 and the insulating cover 24. Accordingly, when the heatedceramic vacuum chuck 42 and the enclosed carrier 36 reach a prescribedtemperature, de-gassed silicone is injected between the carrier 36 andthe mold plate 44 and a thin film of silicone comprising the insulatingcover 24 is created around and between the features of the microcircuits12 while the ring electrode receiving pads 16 of the tail portion 14 andthe interconnect pads 20 of the head portion 18 remain exposed asdepicted in FIGS. 10 and 11. FIG. 10 shows the assembly of FIG. 9 withthe mold plate 44 removed. As an alternative to the overmolding stepsshown in FIGS. 8-10, insulating cover 24 may be provided by laminating asecond layer of film onto the microcircuits 12, adhering the second filmlayer to the microcircuits and to the exposed portions of film substrate22.

After the above-described overmolding process is complete, the carrier36 is placed in a femtosecond laser excising machine (not shown) andusing the vision system built into the laser, the microcircuits areaccurately aligned within the laser. The laser is then activated to cutcompletely through the silicone and nonconductive film layers comprisingthe insulating cover 24 and the film substrate 22 completely freeing themicrocircuits 12 from the carrier 36 as depicted in FIG. 12.

Further processing operations of the process of the present inventionpreferably utilize a tooling bow 46 and a tensioned arbor wire 48extending between opposite free ends of the bow as depicted in FIG. 13A.Basically, the tensioned arbor wire is used to wrap the tail portion 14of one of the newly created microcircuits 12 into a helical shape andalso suspend the electrode assembly 10 through various overmoldingprocesses as will be described below.

In these regards, before installing the arbor wire 48 into the toolingbow 46 a series of the platinum electrode rings 26 are threaded onto thewire 48 prior to its tensioning on the bow. As depicted in FIG. 13A, thehead portion 18 of one of the microcircuits 12 is then threaded onto thearbor wire 48 and clamped in place leaving the tail portion 14 of themicrocircuit 12 free to be manually wrapped on the arbor wire 48. Thisis accomplished by placing the tooling bow 46 into a wrapping fixturealong with the excised microcircuit 12. The tail portion 14 is thenmanually rotated around the arbor wire 48 such that edges of thesilicone cover (or second film layer) 24 and film substrate 22 contacteach other and the tail portion 14 forms a helix on the arbor wire 48 asshown in FIG. 13B. In this regard, FIG. 13B shows the head portion ofthe microcircuit extending from the tensioned wire of the tooling bowand the tail portion wrapped in a helix around the tensioned wire withthe ring electrode receiving pads exposed on an outer surface of thehelix.

It is important that while the tail portion 14 is wrapped on the arborwire 48, the exposed ring electrode receiving pads 16 are wrapped aroundthe silicone cover 24 in proper location or pitch along the tail portionof the microcircuit 12. After wrapping, the platinum electrode rings 26pre-mounted on the arbor wire 48 are positioned by an operator one at atime on the wrapped and exposed receiving pads 16 with radiallyextending holes 27 the electrode rings aligned with the pads for futurelaser welding of the rings to the pads as depicted in FIGS. 14A-C. Inthese regards, after the manual positioning of the platinum rings 26onto the pads 16, the tooling bow 46 is placed into a standard laserwelding machine (not shown) where each electrode ring 26 and hole 27 islocated by the laser vision system of the laser welding machine. Thelaser will then weld each ring 26 to each pad 16 at its ring hole 27 andthe process repeated until all of the electrodes are welded in place.

After laser welding the electrodes 26, the wrapped electrode subassemblyis plasma etched and the preformed microcircuit 12 placed intoovermolding mold tooling. A section 49 of the wrapped electrode up to afirst inactive visual electrode and the underside of the head portion 18shown in FIG. 15 are then encapsulated with a silicone film 50(comprising the overmolded plastic material 28) by overmolding apparatussuch as described and illustrated in FIG. 9. The overmolding of theunderside of the head portion 18 acts as reinforcing for theinterconnect circuit and pads 20 and creates a stand-off that may beused for height referencing when attaching the microcircuit 12 to posts52 extending vertically from a titanium housing 54 as shown in FIGS. 20A and 20B.

After pre-curing the overmold section 49 shown in FIG. 15, the toolingbow 46 is mounted in overmold tooling and placed in overmold apparatussuch as described and illustrated in FIG. 9. A section 60 of the wrappedmicrocircuit 12 shown in FIG. 16 between the overmold of FIG. 15 and themicrocircuit section including the spaced ring electrodes is thenencapsulated in a silicone film 56 depicted in FIG. 16. In this regard,the film 56 in section 60 is feathered down in size creating a smallerdiameter of about 0.025 inches approximately 0.80 inches from the firstinactive visual platinum electrode shown in FIG. 15.

After pre-curing the overmold film 56, the preformed and overmoldedelectrode is removed from the tooling bow 46. As shown most clearly inthe enlarged view of FIG. 17B as well as in FIG. 17A, the electrode isthen unwrapped at a junction 58 with section 60 including the spacedring electrodes, offsetting the electrode section 60 including thespaced ring electrodes and creating a stylet lumen 62. A stylet 64 isinserted in the lumen 62 as illustrated in FIGS. 18A and 18B tostraighten the electrode section 60 and the electrode and stylet areplaced in an overmold apparatus similar to that shown and describedrelative to FIG. 9 where a silicone film 61 is formed encapsulating theelectrode section 60. The completed electrode is then placed in apost-curing oven for final curing of the completed electrode assembly.

When the stylet 64 is removed from the lumen 62, the electrode sectionwill assume the spiral shape shown in FIG. 17A. When it is desired toimplant the electrode assembly, the stylet 64 is re-inserted in thelumen 62 using a conventional stylet insertion tool 66 such as shown inFIG. 18A, FIG. 18B showing the insertion tool 66 rotated 90 degrees toillustrate the handle 67 of the tool.

FIG. 19 shows the completed helix electrode assembly 10 ready forattachment of its head portion 18 to the platinum feedthrough posts 52of the titanium housing 54 as shown in FIGS. 20A and 20B where themicrocircuit interconnect or attachment pads 20 are slit slightly duringlaser machining to make intimate contact with corresponding ones of thefeedthrough posts for laser welding to the posts.

While a preferred embodiment of the cochlear electrode and a for itsmanufacture have been illustrated and described in detail above, it isappreciated that changes and modifications may be made in theillustrated embodiments without departing from the spirit of theinvention. Accordingly, the scope of present invention is to be limitedonly by the terms of the following claims.

1. A process for manufacturing a single microcircuit into an integratedcochlear electrode array, comprising: securing and supporting anonconductive film substrate; attaching a metallic ribbon to a surfaceof the film substrate; machining a flat multiconductor microcircuit fromthe ribbon including (i) a flat elongated multiconductor tail portionwith spaced outwardly exposed electrode receiving pads, and (ii) a flatmulticonductor head portion connected to the tail portion and havingspaced outwardly exposed attachment pads; laminating the flatmicrocircuit between the film substrate and an insulating cover;excising the laminated microcircuit from the film substrate with theelectrode receiving pads exposed; wrapping the tail portion of theexcised laminated microcircuit into a helix with the exposed electrodereceiving pads wrapped around the insulating cover; mounting andelectrically connecting the ring electrodes on and to the exposedelectrode receiving pads; and overmolding the helix tail portion with apolymeric material to ready the microcircuit for cochlear implant. 2.The process of claim 1 wherein the step of excising the laminatedmicrocircuit also exposes the electrode receiving pads.
 3. The processof claim 1 wherein the step of overmolding also includes overmolding anunderside of the head portion.
 4. The process of claim 1 wherein thestep of securing and supporting the film substrate includes tensioningthe film substrate in both an X-axis direction and a Y-axis direction.5. The process of claim 4 wherein the tensioned film substrate isattached to a carrier.
 6. The process of claim 5 wherein the attachmentof the film substrate to the carrier comprises: locating an open lowerframe under the tensioned film substrate and imparting relative verticalmovement between the lower frame and the film substrate until attachmentmeans on the lower frame engage the film substrate, and installing anopen top frame of the carrier on the film substrate over the lowerframe.
 7. The process of claim 6 further including trimming excess filmsubstrate from the carrier.
 8. The process of claim 1 wherein theattaching of the ribbon to the film substrate is proceeded by an etchingof mating surfaces of the ribbon and film substrate followed by loweringof the ribbon onto the film substrate where pressure and heat areapplied for thermal compression attachment of the ribbon to the filmsubstrate.
 9. The process of claim 1 wherein the machining of the flatmulticonductor circuit from the ribbon is by laser cutting of theribbon.
 10. The process of claim 9 wherein the laser cutting is withlight impulses of femtosecond time duration.